Why is playing chess prohibitively disliked?

Chess is makruh tahriman because it is considered a "pointless waste of time" (lahw), and the Prophet (blessings and peace unlimited be upon him) said, "Every pointless waste of time is falsehood." (i.e. impermissible) If there is an actual benefit in the diversion, such as sports for fitness or social bonding, then the relative benefit and harm is weighed (by fuqaha). There are authentic hadiths and reports against chess, and the fuqaha, while admitting some benefits for it, said its overall harm is greater.

This is the ijtihad of the Hanafi school. Others, including the Shafi`is differed. For details, ask a Shafi`i, if you will.

Wassalam,
Faraz.